(1 of )Napa County officials have identified the victim of a fire-related water tender crash Monday as a volunteer firefighter from Missouri named Garrett Paiz. (FACEBOOK)

(2 of )Napa County officials have identified the victim of a fire-related water tender crash Monday as a volunteer firefighter from Missouri named Garrett Paiz. (COURTESY PHOTO)

(3 of ) This June 18, 2017, photo released by Derek Southard, left, shows himself with his father, Daniel Southard, after Derek graduated as a Chemical Engineer from the University of California, Davis, in Sacramento, Calif. The body of Daniel Southard, 71, a retired fitness trainer and high school football coach, was found in his bedroom after wildfires tore through Santa Rosa. (Anna Paseka via AP)

(4 of ) This April, 2017 photo by Brittney Vinculado shows Christina Hanson, with her grandfather Dick Hanson, left, and her father Michael Hanson, in Oakley, Calif. Christina Hanson, 27, used a wheelchair and spent her life dedicated to helping others despite her own hardships, her family said. Kelsi Mannhalter had posted on social media asking people to search for her cousin after the fire Monday ravaged Santa Rosa where Hanson lived. Mannhalter later confirmed on Facebook that Hanson did not survive when the flames consumed her home. (Brittney Vinculado via AP)

(5 of ) In this 2012 photo provided by George Powell shows his wife Lynne Powell picking up her border collie Jemma from the breeder in Grants Pass, Ore. Lynne's car went off the road and into a ravine in the heavy smoke from the Tubbs fire. After searching for her all night and the next day, a detective called to tell George that Lynne's body was found near her car. The couple had been married for 33 years. "I don't know how I'm going to cope. She was my life," said George. (George Powell via AP)

(6 of ) This Saturday, Oct. 7, 2017 photo provided by Jessica Tunis shows her mother, Linda Tunis, at East West Cafe in Santa Rosa. Linda Tunis is among the dead in the wildfires that have been ravaging Northern California. (Jessica Tunis via AP)

(7 of ) In this undated photo provided by Irma Muniz shows the Shepherd family, Jon and Sara Shepherd and their children, Kressa, and Kai. Kai, left, was killed after a wildfire tore through his family's home in Redwood Valley, Calif. on Monday, Oct. 9, 2017. He was 14 when he died, said his aunt, Mindi Ramos. Sara and 17-year-old daughter, Kressa, both sustained burns on 60% of their bodies. Jon sustained burns on 45% of his body. Relatives are trying to raise money to cover medical expenses and prepare to eventually bring the family to live with Sara's parents' home in Redwood Valley. (Irma Muniz via AP)

(8 of ) This undated photo provided by their son Michael Rippey shows Charles and Sara Rippey. Charles, 100, and Sara, 98, were unable to leave their Napa, Calif., home, and died when the Atlas Peak fire swept through. Their bodies were found Monday, Oct. 9, 2017. (Courtesy Michael Rippey via AP)

(9 of ) Karen Aycock

(10 of ) LeRoy, 80, and Donna Halbur, 80, of Angela Drive near Cardinal Newman High School north of Santa Rosa. They died in the first hours of the fast-moving Tubbs fire. The couple had been married for 50 years. (Courtesy photo)

(11 of ) Carmen Caldentey Berriz, 75, of Apple Valley, who died while vacationing in Santa Rosa. The grandmother of six was with her husband of more than 50 years, and both jumped into a swimming pool to try to protect themselves. Only her husband survived. (COURTESY PHOTO)

(12 of ) Dr. Carmen Colleen McReynolds, 82, Santa Rosa. Search crews found that Dr. McReynolds had been trapped inside her 1973 Mercedes-Benz, which was in the burned remains of her garage on Kilarney Circle near the Fountaingrove Golf Club. (GABRIEL COKE/ FACEBOOK)

(13 of ) Sharon Rae Robinson, 79, Santa Rosa. Robinson, who suffered from memory loss, had gone missing after the fire devoured her home on Donner Drive in the Riebli Road area of Santa Rosa early Oct. 9. Her family was concerned when they saw that her car and car were still at her home, and were later notified that Robinson did not survive the fire. (CATHIE MERKEL/ FACEBOOK)

(15 of ) Husband and wife, Arthur Tasman Grant, 95, and Suiko Grant, 75, lived on Sundown Trail in the Mark West neighborhood. "Dad I know you’re back flying a corsair again. Mom, you’ll always be the most beautiful woman in the world to me," their daughter, Trina Grant, said in a Facebook post. (SF Chronicle / Trina Grant)

(16 of ) Roy Howard Bowman, 87, and Irma Elsie Bowman, 88, of Redwood Valley, who died in the Redwood fire. The married couple was found in the remains of their home in the 4000 block of Fisher Lake Drive. Officials said the residence was completely destroyed by the fire.(Facebook / Sharon Barnes Mcmilin)

The tanker went off the road, broke through a guardrail and plunged about 20 feet into a ravine not far from the bottom of the grade and Highway 29, authorities said.

Paiz is a volunteer firefighter with the Noel Fire Department in southwest Missouri but was working as a driver under contract to Cal Fire and would have been unfamiliar with the steep and curving roadway.

The 1993 Kenworth water tender overturned, and the tractor detached from the tanker during the 6:45 a.m. crash, authorities said.